1. Field of the Invention
The present invention relates generally to a bar code reading apparatus for detecting variations in intensity of reflected light from a bar code which is irradiated with laser beams scanned by a scanning optical system. The present invention relates more particularly to a bar code reading apparatus which can automatically decrease intensity of the laser beams and stop the scanning by the scanning optical system when unused.
2. Description of the Prior Art
A practice of managing merchandise and inventory by using bar codes has been popularized in recent years as represented, for example by a POS (point of sale) system in a distribution business. For example, in a POS system of a retail store, items of data such as kinds, sales prices, of the goods, etc. are encoded in a bar code format, and the encoded bar code is printed on the goods or printed on a label affixed to the goods. Then, the bar code is read at a cash register or postern, and the payment of the goods is made based on the read data. Subsequently, the numbers of sales of the goods are determined in real time, which can be useful for stocking, inventory, and purchasing management.
By the way, the above bar code reading apparatus for reading the bar code can be classified into a fixed type used when the goods are relatively small and a hand-held type used when the goods are relatively large. The fixed type involves the use of a mechanism for scanning the bar code with irradiated light beams in multi-directions so that the bar code can be read even when the goods are set over the bar code reader without an operator being aware of a direction of the bar code. More specifically, the fixed type uses a polygon mirror and fixed reflecting mirrors in combination. Laser beams acting as reading irradiated light beams are reflected by a single reflection surface of the polygon mirror, during which these reflected light beams are sequentially incident upon a plurality of fixed reflecting mirrors in order and deflected in a variety of directions for scanning. The bar code reading apparatus receives the reflected light beams from the surface of the goods during such scanning, and decodes the data encoded in the bar code on the basis of variations in intensity of the received light beams.
In this fixed type bar code reader, a laser diode used as a laser light source naturally has a finite usable life. Accordingly, if an emission of the laser beams continues even in a standby status where the reading of the bar code is not carried out although a power is supplied to the laser reading apparatus, the laser diode might require frequent replacement. Similarly, if the optical scanning system is constantly driven, a fault is more likely to occur, and a large quantity of electric power is unnecessarily dissipated.
Conventional bar code reading devices have attempted to solve these problems by utilizing a trigger switch or an item sensor in the vicinity of a bar code reading position (which may be an external surface of a glass plate inset in an outer wall of the bar code reading apparatus so that the laser beams penetrate it toward the outside). In the conventional bar code reading apparatus, an optical scanning system is driven and the laser beams are emitted only when the goods is detected by the trigger switch or the item sensor.
However, in cases where the goods are mechanically detected by the trigger switch or the item sensor, the operator must take steps to make the goods contact with the trigger switch or the item sensor. Hence, the operator has to perform the reading operation while being aware of the trigger switch or the item sensor.